In recent years, portable point of care devices have received increasing interest. Such devices often use capillary forces to propagate fluids in the devices.
These passive microfluidics require a means for controlling the fluid flow. Typically valves, such as capillary trigger valves are used. However, a problem related to such devices is that planar micro-machined capillary trigger valves are unreliable. Increasing the reliability of such valves requires also increasing the complexity of the manufacturing process. To keep the total cost of passive flow devices low, the complexity of the manufacturing process should be minimal.
There is a need for passive flow devices which are able to control the liquid flow without using valves, which are easy to fabricate and which are highly reliable.